Magnetoresistive effect element and magnetic memory device

ABSTRACT

Write characteristics and read characteristics can be improved at the same time by applying novel materials to ferromagnetic layers. In a magnetoresistive effect element having a pair of ferromagnetic layers being opposed to each other through an intermediate layer to cause a current to flow in the direction perpendicular to the film plane to obtain a magnetoresistive change, at least one of the ferromagnetic layers contains a ferromagnetic material containing Fe, Co and B. The ferromagnetic material should preferably contain Fe a Co b Ni c B d  (in the chemical formula, a, b, c and d represent atomic %. 5≦a≦45, 35≦b≦85, 0&lt;c≦35, 10≦d≦30. a+b+C+d=100).

BACKGROUND OF THE INVENTION

The present invention relates to a magnetoresistive effect element forobtaining a magnetoresistive change by causing a current to flow in thedirection perpendicular to the layer plane and a magnetic memory device.

As information communication devices, in particular, personal smalldevices such as personal digital assistants are making great spread,elements such as memories and logics comprising informationcommunication devices are requested to have higher performance such ashigher integration degree, higher operation speed and lower powerconsumption. In particular, technologies for making nonvolatile memoriesbecome higher in density and larger in storage capacity areprogressively increasing their importance as technologies for replacinghard disk and optical disc that cannot be essentially miniaturizedbecause they have movable portions.

As nonvolatile memories, there may be enumerated flash memories usingsemiconductors and FRAM (Ferro electric Random Access Memory) usingferroelectric material and the like. However, the flash memoryencounters with a drawback that its write speed is as slow as themicrosecond order. On the other hand, it is pointed out that the FRAMhas a problem in which it cannot be rewritten so many times.

A magnetic memory device called an MRAM (Magnetic Random Access Memory),which had been written in “Wang et al., IEEE Trans Magn, 33 (1977),4498” receives a remarkable attention as nonvolatile memory which canovercome these drawbacks. Since this MRAM is simple in structure, it canbe easily integrated at a higher integration degree. Moreover, since itis able to memorize information based upon the rotation of magneticmoment, it can be rewritten so many times. It is also expected that theaccess time of this magnetic random access memory will be very high, andit was already confirmed that it can be operated at the access time ofnanosecond order.

A magnetoresistive effect element for use with this MRAM, in particular,a tunnel magnetoresistive (Tunnel Magnetoresistive TMR) element isfundamentally composed of a ferromagnetic tunnel junction offerromagnetic layer/tunnel barrier layer/ferromagnetic layer. Thiselement generates magnetoresistive effect in response to a relativeangle between the magnetizations of the two magnetic layers when anexternal magnetic field is applied to the ferromagnetic layers under thecondition in which a constant current is flowing through theferromagnetic layers. When the magnetization directions of the twomagnetic layers are anti-parallel to each other, a resistance valuebecomes maximum. When they are parallel to each other, a resistancevalue becomes minimum. Function of memory element can be demonstrated bycreating the anti-parallel state and the parallel state with applicationof the external magnetic field.

In particular, in the spin-valve type TMR element, when oneferromagnetic layer is antiferromagnetically coupled to the adjacentantiferromagnetic layer and thereby the magnetization direction isalways made constant, thereby resulting in the same being placed in thestate of a magnetization fixed layer. The other ferromagnetic layer isformed as an information recording layer of which the magnetizationdirection can be easily inverted with application of external magneticfield and the like.

This resistance changing ratio is expressed by the following equation(1) where P1, P2 represent spin polarizabilities of the two magneticlayers.2P1P2/(1−P1P2)  (1)

As described above, the resistance changing ratio increases as therespective spin polarizabilities increase. With respect to arelationship between materials for use with ferromagnetic layers andthis resistance changing ratio, ferromagnetic chemical elements of Fegroup such as Fe, Co, Ni and alloys of three kinds thereof have beenreported so far.

The MRAM is fundamentally composed of a plurality of bit write lines, aplurality of word lines intersecting these bit write lines and TMRelements provided at crossing points between these bit write lines andword write lines as magnetic memory elements as has been disclosed inJapanese laid-open patent application No. 10-116490. Then, wheninformation is written in such MRAM, information is selectively writtenin the TMR element by utilizing an asteroid characteristic.

The bit write line and the word write line for use with the MRAM aremade of conductive thin films such as Cu and Al which areinterconnection materials of ordinary semiconductor devices. Wheninformation is written in a magnetic memory element of which theinverted magnetic field, for example, is 200 Oe by the bit write lineand the word write line made of such ordinary interconnection materials,the bit write line and the word write line being 0.25 μm in width, acurrent of approximately 2 mA is required. When the bit write line andthe word write line have a thickness of 0.25 μm that is the same as theline width thereof, a current density obtained at that time is 3.2×10⁶A/cm³ that is close to approximately a limit value of breaking of wireby electromigration. Accordingly, reduction of the write current isindispensable for maintaining reliability of interconnection. Moreover,in view of a problem of heat generated by the write current and from astandpoint of decreasing power consumption, this write current has to bedecreased.

As a method of realizing the reduction of the write current in the MRAM,there is enumerated a method of decreasing a coercive force of the TMRelement. The coercive force of the TMR element is properly determinedbased upon suitable factors such as the size, shape, layer arrangementof the TMR element and selection of materials. However, when the TMRelement is microminiaturized for the purpose of increasing a recordingdensity of the MRAM, for example, a disadvantage occurs, in which thecoercive force of the TMR element increases. Accordingly, in order tomicrominiaturize (to increase integration degree) of the MRAM and todecrease the write current at the same time, the decrease of thecoercive force of the TMR element should be attained from the materialsstandpoint.

If the magnetic characteristic of the TMR element is dispersed at everyelement in the MRAM and the magnetic characteristic is dispersed whenthe same element is measured repeatedly, then a problem arises, in whichthe selective writing using the asteroid characteristic becomesdifficult. Therefore, the TMR element is requested to have a magneticcharacteristic by which an ideal asteroid curve can be drawn. In orderto draw the ideal asteroid curve, an R-H (resistance-magnetic field)curve obtained when TMR is measured should not have noise such as aBarkhausen noise, a rectangle property of a wave form should beexcellent, the magnetization state should be stable and the dispersionof the coercive force Hc should be small.

Information may be read out from the TMR element as follows. Whenmagnetic moments of one ferromagnetic layer and the other magnetic layeracross the tunnel barrier layer are anti-parallel to each other, thisstate is referred to as a “1”, for example. Conversely, when therespective magnetic moments are parallel to each other, this state isreferred to as a “0”. Information is read out from the element basedupon a difference current obtained at a constant bias voltage or adifference voltage obtained at a constant bias current in these states.Accordingly, when scatterings of resistance between the elements are thesame, a higher TMR ratio is advantageous and hence a memory that canoperate at a high speed, having a high integration degree and having alow error rate can be realized.

Bias voltage dependence of the resistance changing ratio exists in theTMR ratio, and it is known that the TMR ratio decreases as the biasvoltage increases. When information is read out from the element basedupon the difference current or the difference voltage, since it iscustomary for the resistance changing ratio to take the maximum value ofthe read signal at the voltage (Vh) which decreases by half dependingupon the bias voltage dependence, small bias voltage dependence iseffective for decreasing read errors.

As described above, the TMR element for use with the MRAM should satisfythe above-mentioned write characteristic requirements and theabove-mentioned read characteristic requirements at the same time.

However, when the materials of the ferromagnetic layers of the TMRelement are selected, if the alloy compositions by which the spinpolarizabilities shown by P1 and P2 in the equation (1) are increasedare selected from materials made of only ferromagnetic transition metalchemical elements of Co, Fe, Ni, then the coercive force Hc of the TMRelement generally tends to increase.

When the information recording layer is made of a Co₇₅Fe₂₅ (atomic %)alloy or the like, although a TMR ratio having large spinpolarizabilities and which is greater than 40% can be maintained, it isunavoidable that the coercive force Hc also increases.

But instead, when the information recording layer is made of an Ni₈₀Fe₂₀(atomic %) which is what might be called a permalloy that is known as asoft magnetic material, although the coercive force Hc can decrease, thespin polarizabilities are small as compared with the above-mentionedCo₇₅Fe₂₅ (atomic %) alloy so that the TMR ratio is lowered up to about33%.

Moreover, although a Co₉₀Fe₁₀ (atomic %) alloy can produce a TMR ratioof approximately 33% and can suppress the coercive force Hc toapproximately an intermediate value obtained between the above-mentionedCo₇₅Fe₂₅ (atomic %) alloy and the above-mentioned Ni₈₀Fe₂₀ (atomic %)alloy, this alloy is inferior in rectangle ratio of the R-H curve and isunable to provide the asteroid characteristic by which information canbe rewritten in the element.

SUMMARY OF THE INVENTION

In view of the conventional actual circumstances, with application ofnovel materials to the ferromagnetic layers, it is an object of thepresent invention to provide a magnetoresistive effect element and amagnetic memory device in which write characteristics and readcharacteristics can be improved at the same time.

In order to attain the above-mentioned object, in a magnetoresistiveeffect element having a pair of ferromagnetic layers being opposed toeach other through an intermediate layer to cause a current to flow inthe direction perpendicular to the film plane to obtain amagnetoresistive change, according to the present invention, there isprovided a magnetoresistive effect element in which at least one of theferromagnetic layers contains a ferromagnetic layer such as Fe, Co andB.

A magnetic memory device according to the present invention comprises amagnetoresistive effect element having a pair of ferromagnetic layersbeing opposed to each other through an intermediate layer to cause acurrent to flow in the direction perpendicular to the film plane toobtain a magnetoresistive change and word lines and bit lines having themagnetoresistive effect element being sandwiched in the thicknessdirection, in which at least one of the ferromagnetic layers contains aferromagnetic material containing Fe, Co and B.

Since at least one of the ferromagnetic layers contains B in addition toFe and Co that are ferromagnetic transition metal elements as aferromagnetic material, a magnetoresistive (MR) ratio of amagnetoresistive effect element can be increased, a rectangle propertyof an R-H curve can be improved, a bias voltage dependence of an MRratio can be improved, and dispersions of a coercive force can beimproved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view of a main portion andillustrates an example of a TMR element to which the present inventionis applied;

FIG. 2 is a characteristic graph showing resistance-external magneticfield curves of a TMR element having an information recording layer madeof a ferromagnetic material containing Fe, Co, B and a TMR elementhaving an information recording layer made of a ferromagnetic materialcontaining Fe, Co;

FIG. 3 is a schematic cross-sectional view of a main portion of otherexample of a TMR element to which the present invention is applied andillustrates a TMR element including a synthetic ferri-structure;

FIG. 4 is a schematic perspective view of a main portion of across-point type MRAM array that includes a TMR element according to thepresent invention as a memory cell;

FIG. 5 is a cross-sectional view showing a memory cell shown in FIG. 4in an enlarged-scale;

FIG. 6 is a plan view of a TEG that is used to test TMR elements;

FIG. 7 is a cross-sectional view taken along the line A-A in FIG. 6; and

FIG. 8 is a ternary based phase diagram to which reference will be madein explaining an optimum alloy composition of the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

A magnetoresistive effect element and a magnetic memory device to whichthe present invention is applied will be described below in detail withreference to the drawings.

A tunnel magnetoresistive effect element (herein after referred to as a“TMR element”) 1 to which the present invention is applied includes asubstrate 2 made of a suitable material such as Si on which anunderlayer 3, an antiferromagnetic layer 4, a magnetization fixed layer5 which is a ferromagnetic layer, a tunnel barrier layer 6, aninformation recording layer 7 which is a ferromagnetic layer and atop-coat layer 8 are laminated, in that order as shown in FIG. 1, forexample. This TMR element 1 sandwiches the tunnel barrier layer 6 by themagnetization fixed layer 5 and the information recording layer 7 of apair of ferromagnetic layers to form a ferromagnetic tunnel junction 9.The TMR element 1 is of a so-called spin-valve type TMR elementcomprising two ferromagnetic layers one of which is the magnetizationfixed layer 5, the other being the information recording layer 7.

The antiferromagnetic layer 4 is coupled antiferromagnetically to themagnetization fixed layer 5 of one ferromagnetic layer to inhibit themagnetization direction of the fixed magnetization layer 5 from beinginverted so that the magnetization direction of the magnetization fixedlayer 5 may become always constant. Specifically, in the TMR element 1shown in FIG. 1, the magnetization direction of only the informationrecording layer 7 which is the other ferromagnetic layer is invertedwith application of external magnetic fields and the like. As thematerials comprising the antiferromagnetic layer 4, there can be used anMN alloy containing Fe, Ni, Pt, Ir, Rh and the like, Co oxide, Ni oxide,etc.

In the spin-valve type TMR element 1 shown in the figure, themagnetization fixed layer 5 is antiferromagnetically coupled to theantiferromagnetic layer 4 and thereby the magnetization directionthereof can be made constant. Therefore, the magnetization direction ofthe magnetization fixed layer 5 is not inverted even with application ofthe current magnetic field required when information is written in themagnetoresistive effect element.

The tunnel barrier layer 6 can be obtained by oxidizing or nitriding themetal film that has been deposited by a suitable method such as asputtering method and a vapor deposition method. Moreover, the tunnelbarrier layer 6 can also be obtained by a CVD method using organicmetals, ozone, nitrogen, halogen, halogenated gas and the like.

Then, according to the present invention, at least one of themagnetization fixed layer 5 and the information recording layer 7 thatare the ferromagnetic layers of the ferromagnetic tunnel junction 9contains B together with Fe and Co that are ferromagnetic transitionmetal elements as a ferromagnetic material. Although the conventionalTMR element having the ferromagnetic layer composed of onlyferromagnetic transition metals cannot avoid a disadvantage in which acoercive force increases in accordance with an increase of a spinpolarizability, the element according to the present invention containssuch ferromagnetic material, and hence the improvement of the spinpolarizability is compatible with the reduction of the coercive force.Thus, it is possible to improve a TMR ratio and to reduce a writecurrent. In addition, according to the present invention, while a highTMR ratio is being made compatible with a low coercive force, arectangle property of an R-H curve can be prevented from beingdeteriorated. Moreover, since the element according to the presentinvention contains B, it becomes possible to improve bias voltagedependence.

A TMR element having an information recording layer that contains(Co₉₀Fe₁₀)₈₀B₁₀ as a ferromagnetic material and a TMR element having aninformation recording layer that contains Co₉₀Fe₁₀, both of which mayfall within the range of the present invention have been manufactured,respectively, in actual practice, and the results obtained whenresistance-external magnetic field curves of these elements weremeasured are shown in FIG. 2. As is clear from FIG. 2, the TMR elementin which the information recording layer contains Fe, Co, B as theferromagnetic material was able to reduce the coercive force Hc whileholding the TMR ratio at the high level as compared with the TMR elementin which the information recording layer contains only Fe and Co as theferromagnetic material. Moreover, not only a rectangle property of theR-H loop could be improved but also the Barkhausen noise could bedecreased. Therefore, according to the present invention, not only thereduction of the write current becomes possible but also the shape ofthe asteroid curve can be made better and the write characteristic canbe improved so that the reduction of write error becomes possible.

Although causes that can achieve such effects are not clear, it may beconsidered that a microscopic structure in the ferromagnetic layercontaining B changes its tissue form from an ordinary metal tissue tomicrocrystal or amorphous tissue. However, the TMR characteristic cannotalways be improved so long as the microscopic structure is in theamorphous state, and it is important that the ferromagnetic layer shouldcontain the above-mentioned chemical elements and that the ferromagneticlayer should satisfy the range of composition which will be describedlater on.

The alloy composition of Fe, Co, B that the ferromagnetic layer containshas an optimum range, and the ferromagnetic material that at least oneof the magnetic layers contains is composed of a composition formulaFe_(x)Co_(y)B_(z) (in the chemical formula, x, y and z represent atomic%) except for unavoidable impurity chemical elements, wherein 5≦x≦45,35≦y≦85 and 10≦z≦30 should preferably be satisfied. At that time,x+y+z=100 is satisfied. These normal will be described below.

First, B that is added to the ferromagnetic layer will be described. Ifthe added amount of B is less than 10 atomic %, a magneticcharacteristic of Fe—Co alloy that serves as a base is considerablyreflected and only a gentle improvement effect may be achieved.Accordingly, when the ferromagnetic layer contains B of greater than 10atomic %, a TMR ratio can increase considerably and a rectangle ratio ofan R-H curve can be improved as compared with an alloy containing Fe, Coand the like at the same ratio. Since bias dependence of the TMR ratioalso is improved and the magnetization state of the informationrecording layer is further stabilized, a fluctuation of a coercive forceis small and a noise on the R-H curve can be decreased considerably. Theadded amount of B should preferably be under 30 atomic %. If the addedamount of B exceeds 30 atomic %, then ferromagnetic characteristics ofthe information recording layer and the fixed magnetic field of themagnetization fixed layer begin to be degraded. As a consequence, thereare risks that the TMR ratio will be lowered, the rectangle ratio of theR-H curve will be deteriorated and that the coercive force willdecrease. Therefore, in order to achieve the effects of the presentinvention by the addition of B, at least one of the ferromagnetic layersshould preferably contain B which falls within a range of from 10 atomic% to 30 atomic %.

Next, the (Fe, Co) alloy that serves as the base will be described. Froma standpoint of achieving remarkable effects of the present invention,Co is the chemical element indispensable for achieving such effects. Tobe more specific, the alloy composition containing B needs Co of atleast 35 atomic %. This content is selected in order to promote theeffects achieved by the addition of B and also to hold the ferromagneticproperties. If Fe is further added to the above-mentioned alloycomposition, then similarly to the change observed in the Co—Fe basealloy, the TMR ratio can be improved and the coercive force can beincreased. However, the Fe content exceeds 45 atomic %, then thecoercive force increases excessively in the dimension of the element foractual practice, and the resultant product is not suitable for practicaluse as the TMR element. If the Fe content is less than 5 atomic %, thespin polarizability of the ferromagnetic layer is small, and hence thereis a risk that a TMR ratio large enough to enable the element to operateas the magnetoresistive effect element will not be obtained. Therefore,the Fe content should preferably fall within a range of from 5 atomic %to 45 atomic %.

At least one of the ferromagnetic layers of the ferromagnetic tunneljunction of the present invention may contain Ni in addition to Fe, Co,B. Even when the ferromagnetic layer further contains Ni, while theincrease of the coercive force is being suppressed, the satisfactory TMRratio can be maintained, and the improvement effect of the rectangleproperty of the R-H curve can be obtained. The Ni content also has theoptimum range and Ni should preferably fall within a range of from Oatomic % to 35 atomic %. The reason for this is that, if the Ni contentexceeds 35 atomic %, then the coercive force decreases too much, therebymaking it difficult to control an operation of the TMR element.Specifically, the ferromagnetic material that at least one of theferromagnetic layers contains is composed of a composition formulaFe_(a)Co_(b)Ni_(c)B_(d) (in the chemical formula, a, b, c and drepresent atomic %) except unavoidable impurity chemical elements, and5≦a≦45, 35≦b≦85, 0<c≦35, 10≦d≦30 should preferably be satisfied. At thattime, a+b+c+d=100 is satisfied.

While the above-mentioned ferromagnetic material containing Fe, Co, Bmay be applied to at least one of the information recording layer 7 andthe magnetization fixed layer 5, such ferromagnetic material can beapplied to at least the information recording layer 7, more preferably,both of the information recording layer 7 and the magnetization fixedlayer 5 with more remarkable effects of the present invention beingachieved. It is needless to say that other ferromagnetic layers than theferromagnetic layer including ferromagnetic materials containing Fe, Co,B can use materials that are generally used in this kind ofmagnetoresistive effect element.

Moreover, when the above-mentioned materials are applied to theinformation recording layer 7, the film thickness of the informationrecording layer 7 should preferably fall within a range of from 1 nm to10 nm. If the above film thickness falls within this range, thensatisfactory magnetic characteristics can be maintained. The reason forthis is that, if the film thickness of the information recording layer 7is less than 1 nm, then the magnetic characteristics are degradedconsiderably and that if on the other hand the film thickness of theinformation recording layer 7 exceeds 10 nm, then the coercive force ofthe TMR element increases excessively, making this magnetoresistiveeffect element become unsuitable for practical use. However, when theinformation recording layer 7 is not of a single layer composed of alayer made of materials containing the above-mentioned chemical elementsbut has a laminating layer structure composed of a layer made ofmaterials containing the above-mentioned chemical elements and asuitable layer such as an NiFe layer having a small magnetizationamount, for example, it is permitted that the total of the filmthickness of the information recording layer 7 may exceed 10 nm.

When the above-mentioned materials are applied to the magnetizationfixed layer 5, the film thickness of the magnetization fixed layer 5should preferably fall within a range of from 0.5 nm to 6 nm. If thefilm thickness falls within this range, then the effects of the presentinvention can be achieved more reliably. If the film thickness of themagnetization fixed layer 5 is less than 0.5 nm, the magneticcharacteristics are degraded. If on the other hand the film thickness ofthe magnetization fixed layer exceeds 6 nm, there is a risk that asufficient exchange coupling magnetic field between it and theantiferromagnetic layer 4 will not be obtained.

The TMR element of the present invention is not limited to such one inwhich each of the magnetization fixed layer 5 and the informationrecording layer 7 is comprised of a single layer as shown in FIG. 1. Asshown in FIG. 3, for example, even when the magnetization fixed layer 5has the synthetic ferri-structure in which the dielectric layer 5 c issandwiched between a first magnetization fixed layer 5 a and a secondmagnetization fixed layer 5 b, the effects of the present invention canbe achieved. In the TMR element 10 shown in FIG. 3, the firstmagnetization fixed layer 5 a is in contact with the antiferromagneticlayer 4 and the first magnetization fixed layer 5 a is given strongmagnetic anisotropy of one direction by exchange interaction acting onthese layers. As materials for use with the conductive layer 5 c havingthe synthetic ferri-structure, there may be enumerated Ru, Cu, Cr, Au,Ag, etc. for example. Other layers of the TMR element 10 shown in FIG. 3are substantially similar to those of the TMR element 1 shown in FIG. 1.Hence, these layers are denoted by the same reference numerals in FIG. 1and therefore need not be described in detail.

Moreover, it is needless to say that the TMR element 1 of the presentinvention is not limited to the layer arrangements shown in FIGS. 1 and3 and can take various conventional layer arrangements.

Further, the above-mentioned effects can be achieved even when thepresent invention is applied to a spin-valve type magnetoresistiveeffect element having a pair of ferromagnetic layers opposed to eachother through a nonmagnetic conductive layer to cause a current to flowin the direction perpendicular to the film plane to obtain amagnetoresistive change.

The magnetoresistive effect element such as the above-mentioned TMRelement is suitable for use with a magnetic memory device such as anMRAM. The MRAM using the TMR element according to the present inventionwill be described below with reference to FIGS. 4 and 5.

FIG. 4 shows a cross-point type MRAM array including the TRM elementaccording to the present invention. The MRAM array shown in this sheetof drawing includes a plurality of word lines WL and a plurality of bitlines BL that are intersecting these word lines WL and a memory cell 11in which the TMR element of the present invention is disposed at thecrossing point between the word line WL and the bit line BL.Specifically, this MRAM array has 3×3 memory cells 11 disposed in amatrix fashion. It is needless to say that the TMR element for use withthe MRAM array is not limited to the TMR element shown in FIG. 1 and maybe an element having any arrangement such as the TMR element 10 shown inFIG. 3 and which has a synthetic ferri-structure in which one of theferromagnetic layers of the magnetoresistive effect element having thearrangement to cause a current to flow in the direction perpendicular tothe layer surface to obtain a magnetoresistive change contains theabove-mentioned ferromagnetic materials.

Each memory cell 11 includes a silicon substrate 12 on which atransistor 16 composed of a gate electrode 13, a source region 14 and adrain region 15 is provided as shown in FIG. 5, for example. The gateelectrode 13 comprises a read word line WL1. A write word line WL2 isformed on the gate electrode 13 through an insulating layer. A contactmetal 17 is interconnected to the drain region 15 of the transistor 16,and an underlayer 18 is further interconnected to the contact metal 17.This underlayer 18 has the TMR element 1 of the present invention at itsposition corresponding to the upper portion of the write word line WL2.The bit line BL that crosses the word lines WL1 and WL2 at a right angleis formed on this TMR element 1.

Since the MRAM to which the present invention is applied uses the TMRelement 1 in which any one of the ferromagnetic layers comprising theferromagnetic tunnel junction contains specific chemical elements, it isextremely excellent in TMR output and hence stability of memoryoperation can make great improvement. Since the MRAM of the presentinvention uses the TMR element 1 in which the bias voltage dependencecharacteristic of the TMR ratio is improved, the low resistance stateand the high resistance state can be easily distinguished from eachother when information is read out from this memory, and hence the errorrate can decrease. Further, since the noise can decrease in the R-Hcurve and the asteroid characteristic can be improved, the write errorcan decrease. In conclusion, the MRAM of the present invention cansatisfy the read characteristic and the write characteristic at the sametime.

The magnetoresistive effect element such as the TMR element of thepresent invention is not limited to the aforementioned magnetic memorydevice and can also be applied to a magnetic head, a hard disk drivehaving this magnetic head mounted thereon, IC chips, various kinds ofelectronic devices such as personal computers, personal digitalassistants and mobile phones and electric devices.

The present invention is not limited to the above descriptions and mayproperly be modified without departing from the gist of the presentinvention.

INVENTIVE EXAMPLES

Specific inventive examples to which the present invention is appliedwill be described below with reference to the results of experiments.Although switching transistors and the like are available as MRAM inaddition to TMR element as has been set forth with reference to FIGS. 4and 5, according to the inventive examples, in order to examine the TMRcharacteristics, a wafer in which only a ferromagnetic tunnel junctionis formed as shown in FIGS. 6 and 7 had been examined.

Experiment 1

First, we have examined effects achieved by any one of ferromagneticlayer of a ferromagnetic tunnel junction when it contains Fe, Co and Band an optimum range of the composition of the ferromagnetic layer.

<Sample 1>

As shown in FIGS. 6 and 7, in a characteristic evaluation element usedin the inventive examples (Test Element Group: TEG) a word line WL and abit line BL are perpendicular to each other on a substrate 21 and amagnetoresistive effect element 22 is formed at the portion in whichthese word line WL and bit line BL are crossing each other. Themagnetoresistive effect element 22 formed herein is elliptic in shapeand has a minor axis of 0.5 μm×a major axis of 1.0 μm. The word line WLand the bit line BL have terminal pads 23, 24 formed at their respectiveends, and the word line WL and the bit line BL are electricallyinsulated from each other by an insulating film made of Al₂O₃.

Such TEG will be manufactured as follows. First, a word line material isdeposited on the substrate 21 and masked by a photolithography, whereafter other portion than the word line is selectively etched away withapplication of Ar plasma laser and thereby the word line is formed. Atthat time, the region other than the word line was etched away up to 5nm of the depth of the substrate. A silicon substrate with a 0.6mm-thick heat oxide film (2 μm) was used as the substrate.

Next, the ferromagnetic tunnel junction having the following layerarrangement (1), i.e., TMR element was produced on the word line WL by awell-known lithography method and etching. Numerical values within theparentheses indicate film thicknesses.Ta(3 nm)/Cu(100 nm)/PtMn(20 nm)/CoFe(3 nm)/Ru(0.8 nm)/CoFe(2.5 nm)/Al(1nm)−O_(x)/FeCoB(4 nm)/Ta(5 nm)

In the above-described layer arrangement, the composition of FeCoBcomprising the information recording layer was selected to be Fe₉Co₈₁B₁₀(atomic %). The composition of other layer made of CoFe than theinformation recording layer was selected to be Co₇₅Fe₂₅ (atomic %).

The Al—O_(x) layer that serves as the tunnel barrier layer was formed insuch a manner that a metal Al film having a thickness of 1 nm wasdeposited by a DC sputtering method, where after the metal Al film wasoxidized with application of ICP plasma under the condition that theflow rate of oxygen/argon gas was selected to be 1:1, the chamber gaspressure being selected to be 0.1 mTorr. The oxidation time was selectedto be 30 seconds in this inventive example although it may changedepending upon the ICP plasma output.

Other films that the Al—O_(x) layer serving as the tunnel barrier layerwere deposited by a DC magnetron sputtering method.

After the above-described films have been laminated, the resultantproduct was annealed within a field anneal furnace for 4 hours at 270°C. with application of a magnetic field of 10 kOe and the PtMn layerthat is the antiferromagnetic layer was annealed for normalization,thereby resulting in the ferromagnetic tunnel junction being obtained.

After the above-described ferromagnetic tunnel junction has beenmanufactured, an insulating layer 25 having a thickness of about 100 nmwas deposited by sputtering the Al₂O₃ film. Further, the bit lines BLand the terminal pads 24 were formed by the photolithography and therebythe TEG shown in FIGS. 6 and 7 was obtained.

<Sample 2>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₈Co₇₂B₂₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 3>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₇Co₆₃B₃₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 4>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe_(22.5)Co_(67.5)B₁₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 5>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₂₀Co₆₀B₂₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 6>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe_(17.5)Co_(52.5)B₃₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 7>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₃₆Co₅₄B₁₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 8>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₃₂Co₄₈B₂₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 9>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₂₈Co₄₂B₃₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 10>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₂₅Co₇₅ (atomic %) in the layer arrangement (1) of the ferromagnetictunnel junction.

<Sample 11>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₁₀Co₈₂B₈ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 12>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₅₀Co₄₃B₇ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 13>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Co₉₅B₅ (atomic %) in the layer arrangement (1) of the ferromagnetictunnel junction.

<Sample 14>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₁₀Co₅₅B₃₅ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 15>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₃₀Co₃₅B₃₅ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 16>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₄₀Co₃₀B₃₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 17>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₅₀Co₃₀B₂₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

With respect to the TEGs of the thus manufactured samples 1 to 17, theTMR ratios, the dispersions of the coercive force Hc, the rectangleratios and the bias voltage dependences were measured as follows.

Measurement of TMR Ratio:

Although the magnetic memory device such as an ordinary MRAM is able towrite information by inverting the magnetization direction of themagnetoresistive effect element with application of a current magneticfield, in this inventive example, the TMR ratios were measured byinverting the magnetization direction of the magnetoresistive effectelement with application of an external magnetic field. Specifically, anexternal magnetic field for use in inverting the magnetization directionof the information recording layer of the information recording layerwas applied in the direction parallel to the easy axis of magnetizationof the information recording layer. The magnitude of the externalmagnetic field for use in measurement was selected to be 500 Oe. Next,at the same time the magnetoresistive effect element was swept from −500Oe to +500 Oe as seen from one easy axis of magnetization of theinformation recording layer, a tunnel current was caused to flow throughthe ferromagnetic tunnel junction by adjusting a bias voltage such thatthe bias voltage applied to the terminal pad 23 of the word line WL andthe terminal pad 24 of the bit line BL may reach 100 mV. Resistancevalues relative to respective external magnetic fields obtained at thattime were measured. Then, a resistance between a resistance valueobtained in the condition that the magnetizations of the magnetizationfixed layer and the information recording layer are in the anti-parallelstate and that the resistance is high and a resistance value obtained inthe condition that the magnetizations of the magnetization fixed layerand the information recording layer are in the equilibrium state andthat the resistance is low was selected to be the TMR ratio. This TMRratio should preferably be higher than 45% from a standpoint ofobtaining satisfactory read characteristics.

Measurement of Dispersions of Coercive Force Hc:

The coercive force (Hc) was calculated from R-H curves obtained from themeasurement method of the above-described TMR ratio. Then, the R-Hcurves were repeatedly measured 50 times with respect to the sameelement, and the coercive force (Hc) was measured with respect to a halfvalue between the maximum resistance value and the minimum resistancevalue. The fluctuation value was calculated as a μHc/Hc mean value. Fromthe standpoint of improving the write characteristic, the dispersions ofthe coercive force (Hc) should be less than 4%.

Measurement of Rectangle Ratio:

A rectangle ratio of wave form was calculated from the R-H curve.Specifically, the rectangle ratio indicates a value of a ratio betweenR1max-R1min of the R-H curve in a range of the magnetic field from −500Oe to +500 Oe and R2max-R2 min at the zero magnetic field (H=0) uponmeasurement, i.e., (R2max-R2min)/R1max-R1min). From the standpoint ofimproving the write characteristic, the rectangle ratio shouldpreferably be greater than 0.9.

Measurement of Bias Voltage Dependence:

The TMR ratios were calculated by measuring the R-H curves while thebias voltage was being changed at the unit of 10 mV from 100 mV to 1000mV and were plotted relative to the bias voltage. Then, a half biasvoltage relative to the TMR ratio obtained at the extrapolated biasvoltage of 0 mV and the thus obtained bias voltage was set to be Vhalf.The bias voltage Vhalf should preferably be greater than 550 mV.

Compositions and film thicknesses of the information recording layers ofthe above-mentioned samples 1 to 17 are shown on the following table 1.The measured results of thus obtained TMR ratios, the dispersions of thecoercive force Hc, the rectangle ratios and the bias voltage dependencesare shown on the following table 2.

TABLE 1 Film The Fe content The Co content The Ni content The B contentFilm thickness of info. Sample No. arrangement (atomic %) (atomic %)(atomic %) (atomic %) rec. layer (nm) 1 1 9 81 — 10 4 2 1 8 72 — 20 4 31 7 63 — 30 4 4 1 22.5 67.5 — 10 4 5 1 20 60 — 20 4 6 1 17.5 52.5 — 30 47 1 36 54 — 10 4 8 1 32 48 — 20 4 9 1 28 42 — 30 4 10 1 25 75 — — 4 11 110 82 —  8 4 12 1 50 43 —  7 4 13 1 — 95 —  5 4 14 1 10 55 — 35 4 15 130 35 — 35 4 16 1 40 30 — 30 4 17 1 50 30 — 20 4

TABLE 2 Dispersions of Hc value obtained Sample Film TMR when measureRectangle Vhalf No. arrangement ratio (%) repeatedly (%) ratio (mV) 1 146 3.8 0.9 550 2 1 55 1.9 0.92 700 3 1 50 2.4 0.94 620 4 1 50 3.6 0.94560 5 1 58 1.6 0.96 730 6 1 52 2.2 0.96 640 7 1 49 3.8 0.92 560 8 1 561.8 0.93 720 9 1 52 2.5 0.94 610 10 1 42 5.2 0.72 540 11 1 37 4.4 0.83570 12 1 44 5.7 0.86 580 13 1 44 6.6 0.72 590 14 1 28 7.9 0.76 490 15 123 6.4 0.74 510 16 1 19 5.5 0.82 530 17 1 16 4.9 0.79 540

As is clear from the above-mentioned tables 1 and 2, while the samples11 to 13 in which the information recording layer contains a very smallamount of B demonstrate satisfactory values with respect to only thebias voltage dependences, the sample 10 in which any of themagnetization fixed layer and the information recording layer does notcontain B is inferior in all of the TMR ratio, the dispersion of thecoercive force (Hc), the rectangle ratio and the bias voltage dependenceVhalf. From these points, it is to be understood that the writecharacteristic can be improved when at least one of the ferromagneticlayers of the ferromagnetic tunnel junction contains Fe, Co and B.

The samples 1 to 9 of which the alloy compositions fall within the alloycomposition of the present invention demonstrated excellent TMRcharacteristics in which TMR ratios of greater than 45% were obtained,the rectangle ratios of greater than 0.9 being obtained. In the samples1 to 9, the dispersions of the coercive force (Hc) were suppressed to beless than 4%, and hence they are placed in the very stable statemagnetically. Further, in the samples 1 to 9, the bias voltagedependences Vhalf demonstrate values higher than 550 mV, and hence adifference voltage of 0/1 increases when the magnetoresistive effectelement operates as the MRAM. Accordingly, the samples 1 to 9 areexcellent both in the write characteristic and the read characteristic,and hence can realize the MRAM that has very small error wheninformation is written therein and read out therefrom. On the otherhand, it is clear that the samples 10 to 17 which are outside of thecomposition of the present invention are inferior in TMR ratio,dispersion of coercive force (Hc), rectangle ratio and bias voltagedependence Vhalf and that they have unsatisfactory write characteristicand read characteristic.

FIG. 8 is a ternary based phase diagram of Fe, Co, B and shows theirplotted results. Numerical values on this sheet of drawing expresssample numbers. An are a shown hatched in FIG. 8 indicates thecomposition range of the present invention, i.e., the composition rangein which Fe lies within a range of from 5 atomic % to 45 atomic %, Colies within a range of from 35 atomic % to 85 atomic % and B lies withina range of from 10 atomic % to 30 atomic %. The samples 1 to 9 have thecompositions that may fall within these ranges.

From the above-mentioned points, it is to be understood that any one ofthe ferromagnetic layers of the ferromagnetic tunnel junction shouldpreferably contain Fe, Co and B, Fe should preferably fall within arange of from 5 atomic % to 45 atomic %, Co should preferably fallwithin a range of from 35 atomic % to 85 atomic % and that B shouldpreferably fall within a range of from 10 atomic % to 30 atomic %.

Experiment 2

Next, an optimum film thickness range of the information recording layerhas been examined while the layer arrangement of the ferromagnetictunnel junction was being changed.

<Sample 18>

A TEG was obtained by a similar method to that of the sample 1 exceptthat the layer arrangement of the ferromagnetic tunnel junction wasselected to be the following layer arrangement (2) and that thecompositions of the magnetization fixed layer and the informationrecording layer were changed. Specifically, in this sample 18, thecomposition of the magnetization fixed layer was selected to beFe₂₀Co₆₀B₂₀ (atomic %) that may fall within the composition range of thepresent invention. Moreover, the composition of the informationrecording layer in this sample 19 was selected to be Fe₄₅Co₄₅B₂₀ (atomic%). Further, in this sample 18, the film thickness of the informationrecording layer was selected to be 5 nm unlike the samples 1 to 17. Ta(3 nm)/Cu (100 nm)/PtMn(20 nm)/CoFe(3 nm)/Ru(0.8 nm)/CoFe(2 nm)/CoFeB(1nm)/Al(1 nm)−O_(x)/FeCoB(5 nm)/Ta(5 nm)

<Sample 19>

A TEG was obtained by a similar manner to that of the sample 18 exceptthat the composition of the information recording layer was selected tobe Fe₄₀Co₄₀B₂₀ (atomic %) in the layer arrangement (2) of theferromagnetic tunnel junction.

<Sample 20>

A TEG was obtained by a similar manner to that of the sample 18 exceptthat the composition of the information recording layer was selected tobe Fe₃₅Co₃₅B₃₀ (atomic %) in the layer arrangement (2) of theferromagnetic tunnel junction.

<Sample 21>

A TEG was obtained by a similar manner to that of the sample 18 exceptthat the composition of the information recording layer was selected tobe Fe₈Co₇₂B₂₀ (atomic %) in the layer arrangement (2) of theferromagnetic tunnel junction.

<Sample 22>

A TEG was obtained by a similar manner to that of the sample 18 exceptthat the composition of the information recording layer was selected tobe Fe₂₀Co₆₀B₂₀ (atomic %) in the layer arrangement (2) of theferromagnetic tunnel junction.

<Sample 23>

A TEG was obtained by a similar manner to that of the sample 18 exceptthat the composition of the information recording layer was selected tobe Fe₃₂Co₄₈B₂₀ (atomic %) in the layer arrangement (2) of theferromagnetic tunnel junction.

<Sample 24>

A TEG was obtained by a similar manner to that of the sample 18 exceptthat the composition of the information recording layer was selected tobe Fe₄₀Co₄₀B₂₀ (atomic %) in the layer arrangement (2) of theferromagnetic tunnel junction.

<Sample 25>

A TEG was obtained by a similar manner to that of the sample 18 exceptthat the composition of the information recording layer was selected tobe Fe₈Co₇₂B₂₀ (atomic %) in the layer arrangement (2) of theferromagnetic tunnel junction and that the film thickness of theinformation recording layer was selected to be 1.8 nm.

<Sample 26>

A TEG was obtained by a similar manner to that of the sample 18 exceptthat the composition of the information recording layer was selected tobe Fe₂₀Co₆₀B₂₀ (atomic %) in the layer arrangement (2) of theferromagnetic tunnel junction.

<Sample 27>

A TEG was obtained by a similar manner to that of the sample 18 exceptthat the composition of the information recording layer was selected tobe Fe₃₂Co₆₀B₂₀ (atomic %) in the layer arrangement (2) of theferromagnetic tunnel junction.

<Sample 28>

A TEG was obtained by a similar manner to that of the sample 18 exceptthat the composition of the information recording layer was selected tobe Fe₉Co₈₁B₁₀ (atomic %) in the layer arrangement (2) of theferromagnetic tunnel junction and that the film thickness of theinformation recording layer was selected to be 10.5 nm.

<Sample 29>

A TEG was obtained by a similar manner to that of the sample 18 exceptthat the composition of the information recording layer was selected tobe Fe₈Co₇₂B₂₀ (atomic %) in the layer arrangement (2) of theferromagnetic tunnel junction.

<Sample 30>

A TEG was obtained by a similar manner to that of the sample 18 exceptthat the composition of the information recording layer was selected tobe Fe₇Co₆₃B₃₀ (atomic %) in the layer arrangement (2) of theferromagnetic tunnel junction.

Compositions and film thicknesses of the information recording layers ofthe samples 18 to 30 are shown on the following table 3. Moreover, themeasured results of the thus calculated TMR ratios, the dispersions ofthe coercive force Hc, the rectangle ratios and the bias voltagedependences are shown on the following table 4.

TABLE 3 Film The Fe content The Co content The Ni content The B contentFilm thickness of info. Sample No. arrangement (atomic %) (atomic %)(atomic %) (atomic %) rec. layer (nm) 18 2 45 45 — 10 5 19 2 40 40 — 205 20 2 35 35 — 30 5 21 2 8 72 — 20 2.5 22 2 20 60 — 20 2.5 23 2 32 48 —20 2.5 24 2 40 40 — 20 2.5 25 2 8 72 — 20 1.8 26 2 20 60 — 20 1.8 27 232 48 — 20 1.8 28 2 9 81 — 10 10.5 29 2 8 72 — 20 10.5 30 2 7 63 — 3010.5

TABLE 4 Dispersions of Hc value obtained Sample Film TMR when measureRectangle Vhalf No. arrangement ratio (%) repeatedly (%) ratio (mV) 18 247 3.9 0.91 560 19 2 54 2 0.93 710 20 2 50 2.5 0.93 610 21 2 51 1.7 0.93680 22 2 53 1.4 0.97 710 23 2 51 1.6 0.94 700 24 2 50 1.8 0.94 690 25 233 1.7 0.94 510 26 2 31 2 0.91 470 27 2 30 2.2 0.9 460 28 2 44 5.6 0.75530 29 2 47 5.2 0.84 600 30 2 45 5 0.81 600

As is clear from the above-mentioned tables 3 and 4, the samples 25 to27 in which the film thickness of the information recording layer was1.8 nm and the samples 28 to 30 in which the film thickness of theinformation recording layer was 10.5 nm were slightly inferior to thesamples 18 to 24 in any one of the respective characteristics.Accordingly, the film thickness of the information recording layer hasthe optimum range of the film thickness and it is to be understood thatthe film thickness should preferably fall within a range of from 1 nm to10 nm, in particular, within a range of from 2.5 nm to 7 nm.

Experiment 3

Next, magnetoresistive effect elements in which any one of theferromagnetic layers comprising the ferromagnetic tunnel junctionfurther contains Ni in addition to Fe, Co, B will be examined.

<Sample 31>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₂₀Co₃₅Ni₃₅B₁₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 32>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₁₀Co₃₅Ni₃₅B₂₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 33>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₇Co₃₅Ni₂₈B₃₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 34>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₁₅Co₅₀Ni₂₅B₁₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 35>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₁₅Co₄₀Ni₂₅B₂₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 36>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₁₀Co₃₅Ni₂₅B₃₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 37>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₁₀Co₃₅Ni₃₅B₂₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction and that the film thickness of theinformation recording layer was selected to be 2.5 nm.

<Sample 38>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₁₅Co₄₀Ni₂₅B₂₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction and that the film thickness of theinformation recording layer was selected to be 2.5 nm.

<Sample 39>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₂₀Co₃₀Ni₃₀B₂₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

<Sample 40>

A TEG was obtained by a similar manner to that of the sample 1 exceptthat the composition of the information recording layer was selected tobe Fe₅Co₄₀Ni₄₅B₁₀ (atomic %) in the layer arrangement (1) of theferromagnetic tunnel junction.

Compositions and film thicknesses of the information recording layers ofthe samples 31 to 40 are shown on the following table 5. Moreover, themeasured results of the thus calculated TMR ratios, the dispersions ofthe coercive force Hc, the rectangle ratios and the bias voltagedependences are shown on the following table 6.

TABLE 5 Film The Fe content The Co content The Ni content The B contentFilm thickness of info. Sample No. arrangement (atomic %) (atomic %)(atomic %) (atomic %) rec. layer (nm) 31 1 20 35 35 10 4 32 1 10 35 3520 4 33 1 7 35 28 30 4 34 1 15 50 25 10 4 35 1 15 40 25 20 4 36 1 10 3525 30 4 37 1 10 35 35 20 2.5 38 1 15 40 25 20 2.5 39 1 20 30 30 20 4 401 5 40 45 10 4

TABLE 6 Dispersions of Hc value obtained Sample Film TMR when measureRectangle Vhalf No. arrangement ratio (%) repeatedly (%) ratio (mV) 31 145 3.2 0.94 550 32 1 52 1.4 0.97 660 33 1 48 1.9 0.95 600 34 1 44 3.40.93 550 35 1 50 1.7 0.95 690 36 1 46 2.1 0.95 600 37 1 43 2 0.96 580 381 46 1.6 0.96 670 39 1 40 2.1 0.94 560 40 1 36 3.4 0.88 520

As is clear from the above-mentioned tables 5 and 6, it is to beunderstood that the samples 31 to 38 in which the composition ranges ofFe, Co, B fall within the proper ranges could obtain excellent writecharacteristics and excellent read characteristics even when theyfurther contain Ni. However, the sample 40 in which the Ni content was45 atomic % caused the TMR ratio to be lowered, caused the rectangleratio to be deteriorated and caused the bias voltage dependence Vhalf tobe lowered. From these points, it is to be understood that the optimumrange exists in the Ni content and that this content should preferablybe less than 35 atomic %. Moreover, since the TMR ratio was lowered inthe sample 39 in which the Co content is insufficient, it is to beunderstood that the Fe and Co contents are important as the alloy whichserves as the base of the ferromagnetic layer.

As set forth above, according to the present invention, by improving theMR ratio, the rectangle property of the R-H curve, the bias voltagedependence of the MR ratio and the dispersion of the coercive force, itis possible to provide a magnetoresistive effect element that cansatisfy the write characteristic and the read characteristic at the sametime when it is applied for use with a magnetic memory device and thelike.

Furthermore, by using such magnetoresistive effect element, it ispossible to realize a magnetic memory device that can satisfy the writecharacteristic and the read characteristic at the same time.

1. A magnetic memory device comprising: a magnetoresistive effectelement having a pair of ferromagnetic layers opposed to each otherthrough an intermediate layer to cause a current to flow in thedirection perpendicular to the layer plane to obtain a magnetoresistivechange; and word lines and bit lines having said magnetoresistive effectelement sandwiched in the thickness direction, wherein, at least one ofsaid ferromagnetic layers contains a ferromagnetic material containingFe, Co and B, and said ferromagnetic material containsFe_(a)Co_(b)Ni_(c)B_(d), where a, b, c and d represent atomic % and5≦a≦45, 35≦b≦85, 0≦c≦35, 10≦d≦30 and a+b+C+d=100.
 2. A magnetic memorydevice according to claim 1, wherein said ferromagnetic materialcontains Fe_(x)Co_(y)B_(z), where x, y and z represent atomic % and5≦x≦45, 35≦y≦85, 10≦z≦30 and x+y+z=100.
 3. A magnetic memory deviceaccording to claim 1, wherein said ferromagnetic material is amorphous.4. A magnetic memory device according to claim 1, wherein saidmagnetoresistive effect element is a tunnel magnetoresistive effectelement using a tunnel barrier layer as said intermediate layer.
 5. Amagnetic memory device according to claim 1, wherein saidmagnetoresistive effect element is a spin-valve type magnetoresistiveeffect element in which one of said ferromagnetic layers is amagnetization fixed layer, the other one being an information recordinglayer.
 6. A magnetic memory device according to claim 1, furtherincluding a synthetic ferri-structure.